Methods for electrochemical hydrogenation and methods of forming membrane electrode assemblies

ABSTRACT

A method for electrochemical hydrogenation comprises introducing an organic feed material to an electrochemical cell. The electrochemical cell comprises a membrane electrode assembly comprising an anion exchange membrane, a cathode in electrical contact with a first side of the anion exchange membrane, and an anode in electrical contact with a second side of the anion exchange membrane opposite the first side of the anion exchange membrane. A current passes through the membrane electrode assembly to convert molecules in the organic feed material to a reduced product comprising reduced molecules containing a higher proportion of hydrogen than the organic feed material. A method of forming a membrane electrode assembly comprises forming an ink mixture comprising carbon and a resin, providing droplets of the ink mixture on a substrate to form a decal, and disposing the decal in contact with an anion exchange membrane.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No. 62/719,989, filed Aug. 20, 2018, for “Methods for Electrochemical Hydrogenation and Methods of Forming Membrane Electrode Assemblies,” the disclosure of which is hereby incorporated herein in its entirety by this reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under Contract Number DE-AC07-05-ID14517, awarded by the United States Department of Energy. The government has certain rights in the invention.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to electrochemical cells, such as for hydrogenation of organic chemicals.

BACKGROUND

Biomass-derived fuels and chemicals are a sustainable alternative to fuels and chemicals derived from petroleum that leverage many of the advantages those fuels possess (such as energy density, rapid fueling, existing infrastructure, mature technology, etc.). The substitution of fossil resources typically requires the production of commodity chemicals that can be obtained from the comprehensive processing of biomass through three main steps: preprocessing, valorization, and refinement.

Biomass-derived platform molecules (BDPM) can be obtained after biomass is pre-processed through fractionation and/or deconstruction of cellulose, hemicellulose, and lignin, which are major constituents of lignocellulosic biomass. The BDPMs may be used to replace conventional hydrocarbons derived from non-renewable sources, such as fossil fuels. However, there are differences between BPDMs and the building blocks of petrochemical materials that make up the majority of currently consumed hydrocarbons for energy production. The differences between BDPMs and petrochemical building blocks, are generally due to the nature and composition of the original sources (e.g., oxygen, carbonyls, and phenolic groups). Unfortunately, such differences between BPDMs and the petrochemical building blocks translate into poor physicochemical characteristics for incorporation of the BDPMs into current refinery infrastructure.

Oxygenated compounds exhibit higher boiling points than hydrocarbons having a similar number of carbon atoms, and the boiling points significantly vary with the degree of oxygenation, polarity, and functional groups rather than with the number of carbons. On the other hand, higher density of oxygenated molecules could impact the economy of the refining industry, in which sales are performed based on volumetric quantities. Therefore, a method for transforming BDPMs into molecules that better fit a refining process would be beneficial.

BRIEF SUMMARY

In some embodiments, a method for electrochemical hydrogenation comprises introducing an organic feed material to an electrochemical cell. The electrochemical cell comprises a membrane electrode assembly comprising an anion exchange membrane, a cathode in electrical contact with a first side of the anion exchange membrane, and an anode in electrical contact with a second side of the anion exchange membrane opposite the first side of the anion exchange membrane. A current passes through the membrane electrode assembly to convert molecules in the organic feed material to a reduced product comprising reduced molecules containing a higher proportion of hydrogen than the organic feed material.

In other embodiments, a method of forming a membrane electrode assembly comprises forming an ink mixture comprising carbon and a resin, providing droplets of the ink mixture on a substrate to form a decal, and disposing the decal in contact with an anion exchange membrane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified schematic view illustrating a membrane electrode assembly, according to a method of the present disclosure.

FIG. 2 is a simplified schematic view illustrating an electrochemical system that includes the membrane electrode assembly of FIG. 1, according to embodiments of the disclosure.

FIG. 3 illustrates chemical structures of some molecules that may be reacted in electrochemical systems disclosed herein.

FIG. 4 is a simplified schematic view illustrating a continuous electrochemical system that includes the membrane electrode assembly of FIG. 1, according to embodiments of the disclosure.

DETAILED DESCRIPTION

The illustrations presented herein are not actual views of any particular process or system, but are merely idealized representations that are employed to describe example embodiments of the present disclosure. Additionally, elements common between figures may retain the same numerical designation.

FIG. 1 is a simplified schematic view of a membrane electrode assembly 100 (MEA) useful for electrochemical hydrogenation. The membrane electrode assembly 100 includes an anion exchange membrane 102, a cathode 104, and an anode 106. Electrodes (i.e., cathodes and anodes) and anion exchange membranes may be fabricated by methods known in the art or as described below. The cathode 104 and the anode 106 are attached to opposite sides of the anion exchange membrane 102. The cathode 104 and the anode 106 may be separated only by the anion exchange membrane 102 in a zero-gap configuration. In other words, the cathode 104 may directly contact the anion exchange membrane 102 and the anode 106 may directly contact the anion exchange membrane 102. The zero-gap configuration may limit or minimize the voltage drop between the electrodes and may eliminate the need to add a supporting electrolyte to the material to be electrolyzed. Stated another way, since the cathode 104 and the anode 106 directly contact the anion exchange membrane 102 and are separated from each other only by the anion exchange membrane 102, in some embodiments, the membrane electrode assembly 100 may not include an electrolyte. In some such embodiments, anions may be exchanged through the anion exchange membrane 102 without a supporting electrolyte.

In some embodiments, the cathode 104 and the anode 106 may be bonded to the anion exchange membrane 102. In other embodiments, the cathode 104 and the anode 106 may be physically pressed against the membrane.

In yet other embodiments, the cathode 104 and the anode 106 are physically separated from the anion exchange membrane 102. The cathode 104 and the anode 106 described herein may be comprised of, or include, various selected materials and compositions including, but not limited to, for example, metals, carbon, various metals on carbon supports, various metal oxides on carbon supports or metal supports, various conductive composite materials, and combinations of these various materials as will be understood by those of skill in the electrochemical arts.

The cathode 104 may include one or more of carbon or a metal. By way of non-limiting example, the cathode 104 may include carbon black, carbon fibers, carbon nanotubes, graphene, or any other form of carbon. In some embodiments, the cathode 104 may include a carbon powder material, such as VULCAN® XC72R, available from Cabot Corporation, of Boston, Mass. In some embodiments, the cathode 104 includes carbon and one or more catalyst materials, such as one or more of platinum, palladium, rhodium, ruthenium, nickel, iridium, titanium copper, gold, or silver. The cathode 104 may include or more fluorinated polymers (fluoropolymers), one or more chlorinated polymers (chloropolymers), or both. The polymers may include the carbon and catalyst materials therein.

The cathode 104 may include one or more hydrophobic molecules, such as polytetrafluoroethylene. By way of non-limiting example, the cathode 104 may include one or more of carbon, polytetrafluoroethylene (PTFE) (such as Teflon produced by DuPont of Midland, Mich.), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), perfluoroalkoxy polymer (PFA), fluorinated ethylene-propylene (FEP), polyethylenetetrafluoroethylene (ETFE), polyethylenechlorotrifluoroethylene (ECTFE), perfluorinated elastomer (FFPM), perfluorosulfonic acid (PFSA), polyvinyl chloride (PVC), or poly(dichlorophosphazene), polyvinylidene chloride. In some embodiments, the cathode 104 includes a hydrophobic coating formed of the one or more hydrophobic molecules. In some embodiments, the cathode 104 comprises polytetrafluoroethylene.

The anode 106 may include one or more of carbon, one or more metals, such as one or more of titanium, iridium, iridium oxide, rhodium, rhodium oxide, platinum, platinum oxide, or another metal or metal oxide. In some embodiments, the anode 106 comprises titanium and one or more of iridium, iridium oxide, rhodium, rhodium oxide, platinum, platinum oxide. In some embodiments, the anode 106 comprises titanium plated with platinum.

The anion exchange membrane 102 may include a polymer functionalized with one or more amines. The anion exchange membrane 102 may comprise a polymeric membrane that contains covalently bound cations, such as one or more of quaternary ammonium cations, tertiary diamine anions, or other anions. In some embodiments, the anion exchange membrane 102 comprises functionalized polytetrafluoroethyle, polyethylene, or both.

As depicted in FIG. 1, a reaction feed material 108 may react at the cathode 104 to form a reaction product 110. The reaction feed material 108 may include, for example, an oxygenated organic compound, such as one or more BDPMs. In some embodiments, the reaction feed material 108 may be a biomass material. By way of nonlimiting example, the reaction feed material 108 may include one or more of ethanol, glycerol, xylitol, sorbitol, lactic acid, hydroypropanoic acid, levulinic acid, succinic acid, furfural, hydroxymethylfurfural, furandicarboxylic acid, isoprene, acetic acid, acetonitrile, acetophenone, guaiacol, phenol, benzaldehyde, p-methooxythiopenol, valeraldehyde, or dimethylformamide. However, the disclosure is not so limited and the reaction feed material 108 may include materials other than those described. Typically, the reaction product 110 includes one or more compounds that are hydrogenated (i.e., reduced) as compared to the reaction feed material 108.

The reaction feed material 108 may be mixed with a solvent which may be formulated and configured to provide hydrogen, protons, or both to the reaction feed material 108 (e.g., to the BDPMs). The solvent may include, for example, one or more of water, acetic acid, or an organic solvent including hydrogen atoms (e.g., acetone, dimethylformamide (DMF), dimethylsulfoxide (DMSO), pentane, hexane, benzene, diethyl ether, alcohols (methanol, ethanol, isopropyl alcohol, butanol, furfuryl alcohol, pentanol, etc.), esters (e.g., methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl butyrate, ethyl butyrate, pentyl acetate, isopentyl acetate, benzyl acetate, pentyl butyrate, octyl acetate, etc.), amines (methylamine, ethylenediamine, propylamine, pyrrolidine, diethylamine, diethylenetriamine, piperidine, pyridine, tributylamine, etc.)). In some embodiments, the organic solvents are dispersed in a non-aqueous media or in an aprotic media (e.g., acetonitrile). In some embodiments, the reaction feed material 108 is mixed with water. In some such embodiments, the water may be used to generate hydrogen and hydroxide anions via Reaction (1) below:

2H₂O+2e ⁻→H₂+2OH⁻;  Reaction (1).

As further depicted in FIG. 1 at arrow 114, the anions may flow through the anion exchange membrane 102 from the cathode 104 to the anode 106, and may be driven by a current applied by a power source 112. At the anode 106, the hydroxide anions may react to form water and oxygen via Reaction (2) below:

4OH⁻→2H₂O+O₂+4e ⁻;  Reaction (2).

As indicated by arrow 116, electrons may flow from the anode 106 to the cathode 104 via an external circuit, such as the power source 112.

The membrane electrode assembly 100 may be used in an electrochemical system 200, shown in FIG. 2. The membrane electrode assembly 100, in combination with chambers 202, 204, may form an electrochemical cell 206. The chamber 202 may be configured such that fluid therein is in contact with the cathode 104 (FIG. 1) and the chamber 204 may be configured such that fluid therein is in contact with the anode 106 (FIG. 1). The power source 112 may be electrically connected to the electrochemical cell 206.

The chamber 202 may include the reaction feed material 108, which may be configured to be in fluid contact with the cathode 104. In some embodiments, the chamber 202 comprises serpentine channels for providing contact between the feed material 108 and the cathode 104. The chamber 204 may comprise serpentine channels for providing contact between a feed 208 and the anode 106. The chambers 202, 204 may each comprise a titanium flow plate.

The electrochemical system 200 may include piping, pumps, or other appropriate flow equipment to deliver the reaction feed material 108 to the chamber 202 (and the cathode 104). For example, pump 201 may be configured to deliver the reaction feed material 108 to the chamber 202. The electrochemical system 200 may also include piping, pumps, or other appropriate flow equipment to deliver a feed 208 (e.g., a liquid or gas, such as water, an organic material, hydrogen, chlorine, etc.) to the chamber 204 (and the anode 106).

The electrochemical system 200 may be used to perform electrolysis by introducing an organic feed material (i.e., the reaction feed material 108) to the electrochemical cell 206, introducing the feed 208 to the electrochemical cell 206, and passing a current through the membrane electrode assembly 100 to convert molecules in the organic feed material to a reduced product (i.e., the reaction product 110 or a component thereof) comprising reduced molecules containing a higher proportion of hydrogen than the organic feed material.

The power source 112 may apply a potential to the electrodes (between the cathode 104 and the anode 106) that is sufficiently high to cause electrons to flow to, or from, the electrodes present in the electrochemical cell 206. For example, application of a potential to the electrochemical cell 206 may cause electrons to flow from the anode 106 to the cathode 104. In operation, a sufficiently high potential during electrolysis may be attained by controlling either the applied potential or the applied current that flows through the electrochemical cell 206. By way of nonlimiting example, a current density applied to the cathode 104 and the cathode 106 may be within a range of from about 0.1 mA/cm² to about 1.0 A/cm², such as from about 0.1 mA/cm² to about 0.5 mA/cm², from about 0.5 mA/cm² to about 1.0 mA/cm², from about 1.0 mA/cm² to about 5.0 mA/cm², from about 5.0 mA/cm² to about 10.0 mA/cm², from about 10.0 mA/cm² to about 50 mA/cm², from about 50 mA/cm² to about 100 mA/cm², from about 100 mA/cm² to about 250 mA/cm², from about 250 mA/cm² to about 500 mA/cm², or from about 500 mA/cm² to about 1 A/cm².

Potentials and currents delivered to the electrochemical cell 206 may be steady, ramped, or pulsed. In some embodiments, the cathode half-cell reaction provides reduction of the reaction feed material 108 and the anode half-cell reaction provides oxidation of hydroxide anions that pass through the membrane electrode assembly 100 (i.e., from the cathode 104, through the anion exchange membrane 102, to the anode 106 and the chamber 204). The feed 208 may serve as a medium in which the anions can react. In other embodiments, the anode reaction may provide other oxidation reactions including, for example, oxidation of water (e.g., wastewater, such as water including ammonia dissolved therein), oxidation of H₂, oxidation of organics (e.g., alcohols (methanol, ethanol, propanol, etc.), other organic molecules), or oxidation of chloride to chlorine gas. In some embodiments, the feed 208 comprises water.

Electrolysis in the electrochemical system 200 may be performed at relatively low temperatures, such as between about 0° C. and about 100° C., between about 15° C. and about 75° C., or even between about 20° C. and about 50° C. In some embodiments, the electrolysis in the electrochemical system 200 is performed at ambient temperature, such as a temperature within a range from about 20° C. to about 25° C. Furthermore, the electrolysis may be performed at relatively low pressures, such as less than about 10 MPa, less than about 5 MPa, less than about 2 MPa, or even less than about 1 MPa. In some embodiments, the electrolysis is performed at a pressure less than about 0.5 MPa, such as at ambient pressure.

The reaction feed material 108 may include an organic feed material, as described above, and water or an organic solvent (e.g., ethanol, acetic acid, acetonitrile, dimethylformamide, etc.). For example, the reaction feed material 108 may include one or more of the organic compounds shown in FIG. 3, which are common BDPMs and petrochemicals.

The electrochemical system 200 may further include a vessel 210, which may be configured to separate gaseous phase materials from liquid phase materials. In some embodiments, the vessel 210 comprises a phase separator (e.g., a splitter). The vessel 210 may be configured to separate gaseous materials from liquid materials. For example, in some embodiments, hydrogenation may form the reaction product 110 to comprise at least some vapor components 212. In some such embodiments, the vapor components 212 may be separated from the liquid components in the vessel 210. In some embodiments, the reaction feed material 108 is recirculated under a desired amount of the reaction feed material 108 has been hydrogenated.

During electrolysis, electrons flowing to the cathode 104 may cause the water in the reaction feed material 108 to form hydrogen and hydroxide ions according to Reaction (1) described above. The hydroxide ions may pass through the anion exchange membrane 102, and the hydrogen may react with the organic feed material at or near the cathode 104. The membrane electrode assembly 100 may include a catalyst (e.g., as part of the cathode 104) formulated to promote the hydrogenation of the organic feed material. The catalyst may include, for example, one or more of platinum, palladium, rhodium, ruthenium, nickel, iridium, titanium copper, gold, or silver. For example, the cathode 104 may include polytetrafluoroethylene (PTFE), which is a hydrophobic molecule, to cause the selective reduction of organic molecules as compared to reduction of water molecules. In some embodiments, the hydrophobic material may contribute to control of the mass transfer of water to active sites, enhancing the reduction of the organic molecules in preference to the hydrogen evolution reaction (e.g., the generation of hydrogen from protons).

The addition of hydrophobicity (e.g., through the inclusion of PTFE in the cathode 104) may help control the mass transfer of water to the active sites on the catalyst, which may enhance the reduction of the organic molecules in comparison with hydrogen evolution. Because hydrogen evolution is the main competing reaction in organic hydrogenation, use of the hydrophobic material (e.g., the polytetrafluoroethylene) in the cathode 104 may increase reaction efficiency of the hydrogenation reaction.

The hydroxide ions may be passed through the anion exchange membrane 102 from the cathode 104 to the anode 106. At the anode 106, the hydroxide anions may react to form water and oxygen according to Reaction (2) described above. Electrons may flow from the anode 106 (FIG. 1) to the cathode 104 (FIG. 1) via the power source 112. The water may be removed from the electrochemical system 200, as indicated at 214.

Compared to conventional hydrogenation reactions, the process described herein may increase the selectivity for organic reduction over hydrogen gas production. For example, and by way of comparison, hydrogenation reactions using proton exchange membranes require generation of protons (W) at the anode (via the oxidation of water and/or hydrogen gas) and transfer of the protons from the anode to the cathode through cation exchange membranes. However, the protons may react with each other to form hydrogen gas during transport of the protons from the anode to the cathode, reducing the efficiency of the electrochemical cell (since the hydrogenation reaction requires hydrogen gas). In other words, the consumption of protons to form hydrogen reduces the efficiency of the hydrogenation reaction in conventional electrochemical cells in which the protons are transferred from the anode to the cathode. By way of contrast, the hydrogen for the hydrogenation reaction described herein is generated directly in the chamber 202 in contact with the cathode 104 and from a material (e.g., water) within the cathode solution. Accordingly, the hydrogen (or protons) does not need to transfer through a membrane (e.g., the anion exchange membrane 102). Further, and without being bound by any particular theory, it is believed that a higher pH is generated in the chamber 202 relative to conventional hydrogenation systems including a cation exchange membrane. The higher pH may contribute to a reduced degree of hydrogen evolution reaction.

In addition, water is not substantially transferred from the anode to the cathode through the anion exchange membrane 102, as may be the case when the membrane comprises a cation exchange membrane or a proton exchange membrane. For example, conventional cells including cation exchange membranes often result in the transfer of water from the anode to the cathode, resulting in undesired dilution of the water-soluble organic feed material. Since water transfer occurs in the direction of ion transfer in cells comprising a cation exchange membrane, the catholyte may be continuously diluted through the transfer of water from the anode to the cathode.

Furthermore, in some embodiments, the hydrogen source may comprise one or more of the solvent described above with reference to the reaction feed material 108 (e.g., one or more of water, acetic acid, or an organic solvent, such as one or more of an alcohol, an ester, or an amine) and the reaction may be performed without addition of external hydrogen, and the process can be operated at low pressure and temperature conditions. Given the reduced infrastructure needs for the process as compared to conventional hydrogenation processes, (the process disclosed herein may be operated with electricity as the only utility) this process opens up options for processing outside large refineries and reduces need for natural-gas reforming to produce hydrogen.

Although FIG. 2 illustrates the electrochemical system 200 comprising a batch system, the disclosure is not so limited. In other embodiments, the electrochemical system 200 may comprise a continuous system for hydrogenating the reactor feed material 108. FIG. 4 illustrates an electrochemical system 400 that may operate continuously. The electrochemical system 400 may include the same materials and structures as the electrochemical system 200. In some embodiments, a degree of hydrogenation of the reaction feed material 108 may be determined based, at least in part, on a length of the fluid path through the chamber 202.

The membrane electrode assembly 100 shown in FIG. 1 may be formed using an ink mixture. In particular, an ink mixture may be formed to have carbon and a resin. Droplets of the ink mixture may be provided on a substrate to form a decal (e.g., a design prepared on a substrate for transfer onto another surface), and the decal may be disposed in contact with the anion exchange membrane 102. The decal (or multiple decals) may form the cathode 104, the anode 106, or both. The substrate may comprise an anion exchange material, a carbon paper, or another material. In some embodiments, the substrate comprises one or more of the materials described above with reference to the cathode 104.

The ink mixture may be formed and applied in an air gun, a sprayer, an ink-jet printer, or any other device. For example, the carbon and the resin may be mixed with one or more solvents (e.g., water, an alcohol, a hydrocarbon, etc.) and optionally, other additives (e.g., PTFE, metals, etc.). The carbon may include, for example, carbon black, carbon fibers, carbon nanotubes, graphene, or any other form of carbon. In some embodiments, the carbon includes particles of metal catalysts (e.g., one or more of platinum, palladium, rhodium, ruthenium, nickel, iridium, titanium copper, gold, or silver) disposed on at least some surfaces thereof. In some embodiments, the carbon may be VULCAN® XC72R, available from Cabot Corporation, of Boston, Mass. The resin may include an ionomer, such as one or more of nafion (a sulfonated tetrafluoroethylene based fluoropolymer-copolymer, which is a cation exchange ionomer) fumion (an anion exchange ionomer), PTFE, or Fumion and PTFE. The ink mixture may be formulated to have a weight ratio of carbon to resin from about 2:1 to about 10:1, such as about 4:1.

The droplets of the ink mixture may have a volume between about 1 μL and about 20 μL, such as about 8 μL, and may vary based on the size of the electrode to be formed. The droplets may be sprayed onto the substrate to form a uniform coating. If the ink mixture includes a solvent or other volatile material, the ink mixture may be dried during or after application of the droplets to the substrate. For example, the droplets may be air-dried.

If the decal is formed on a substrate other than the anion exchange membrane 102, the decal may be placed in contact with the anion exchange membrane 102 after formation of the decal. In some embodiments, the decal may be hot-pressed against the anion exchange membrane 102 by applying heat and pressure. For example, a pressure of at least 1 MPa may be applied to the decal. In some embodiments, the decal and/or the anion exchange membrane 102 may be heated to a temperature of between about 60° C. and about 150° C. before applying the decal, such as between about 90° C. and about 120° C. If decals are used to form both the cathode 104 and the anode 106, the decals may be applied simultaneously or in series. The cathode 104 and the anode 106 may be applied to opposite sides of the anion exchange membrane 102. Hot-pressing the decal against the anion exchange membrane 102 may facilitate transfer of the ink (e.g., the resin and the carbon) to the anion exchange membrane 102. Hot-pressing may facilitate improved contact between the cathode 104 and the anion exchange membrane 102 and between the anode 106 and the anion exchange membrane 102.

EXAMPLES Example 1: Membrane Electrode Assembly Preparation

Electrocatalyst ink was prepared with VULCAN® XC72R carbon. A solution of 5 wt % Nafion perfluorinated resin (available from Sigma-Aldrich, of St. Louis, Mo.) was used as a cation exchange ionomer. The carbon and the ionomer solution were mixed in butyl acetate, then sonicated for 30 min. After sonication, a 60% PTFE suspension in water was added to the catalyst ink formulation, followed by agitation with a stir bar for an additional 30 min. The quantities of ionomer and PTFE added to the electrocatalyst were estimated to obtain a final electrocatalyst layer with 80 wt % carbon and 20 wt % ionomer/binder.

The cathode catalyst ink was painted on both sides of a sheet of carbon paper. The painted carbon electrode with catalyst loading of about 3 mg/cm² was hot-pressed onto a Fumasep FAA-3-PK-130 membrane opposite a Pt-plated sintered titanium sheet (an anode). The materials were pressed for 90 seconds at 120° C. and 4.8 MPa of pressure.

Example 2: Electrochemical Hydrogenation of Furfural

Flow cell tests were performed using a 10 cm² membrane electrode assembly as described in Example 1. The membrane electrode assembly was pressed against two titanium flow plates with serpentine channels to form an electrochemical cell. On the cathode side, 0.1 M furfural solutions were circulated in the presence and absence of acid electrolyte, while 1 M KOH was fed to the anode to avoid electrode oxidation. The furfural reached nearly complete conversion to reduced products (including dimerized compounds) within the first 30 min of reaction.

Additional examples are shown in “Anion Exchange Membrane Electrolyzers as Alternative for Upgrading of Biomass-Derived Molecules,” Luis A. Diaz et al., ACS Sustainable Chem. Eng. 2018, 6, 8458-8467, the entire disclosure of which is incorporated herein by this reference.

Example 3: Anion Exchange Membrane Preparation

Electrocatalyst ink was prepared with VULCAN® XC72R carbon. A solution of 5 wt % Fumion resin (available from Sigma-Aldrich, of St. Louis, Mo.) was used as an anion exchange ionomer. The carbon and the ionomer solution were mixed in butyl 1-propanol, then sonicated for 30 min. After sonication, a 60% PTFE suspension in water was added to the catalyst ink formulation, followed by agitation with a stir bar for an additional 30 min. The quantities of ionomer and PTFE added to the electrocatalyst were estimated to obtain a final electrocatalyst layer with 80 wt % carbon and 20 wt % ionomer/binder.

The cathode catalyst ink was painted on both sides of a sheet of carbon paper. The painted carbon electrode with catalyst loading of about 3 mg/cm² was hot-pressed onto a Fumasep FAA-3-PK-130 membrane opposite a Pt-plated sintered titanium sheet (an anode). The materials were pressed for 90 seconds at 120° C. and 4.8 MPa of pressure.

Additional non limiting example embodiments of the disclosure are described below.

Embodiment 1

A method for electrochemical hydrogenation, the method comprising introducing an organic feed material to an electrochemical cell. The electrochemical cell comprises a membrane electrode assembly comprising an anion exchange membrane, a cathode in electrical contact with a first side of the anion exchange membrane, and an anode in electrical contact with a second side of the anion exchange membrane opposite the first side of the anion exchange membrane. A current passes through the membrane electrode assembly to convert molecules in the organic feed material to a reduced product comprising reduced molecules containing a higher proportion of hydrogen than the organic feed material.

Embodiment 2

The method of Embodiment 1, wherein passing a current through the membrane electrode assembly comprises passing a current through the membrane electrode assembly at a temperature of between about 0° C. and about 100° C.

Embodiment 3

The method of Embodiment 1 or Embodiment 2, wherein passing a current through the membrane electrode assembly comprises passing a current through the membrane electrode assembly at a pressure of less than about 1 MPa.

Embodiment 4

The method of any of Embodiments 1 through 3, wherein passing a current through the membrane electrode assembly comprises passing hydroxide ions through the anion exchange membrane from the cathode to the anode.

Embodiment 5

The method of any of Embodiments 1 through 4, wherein introducing the organic feed material comprises flowing the organic feed material continuously into the electrochemical cell.

Embodiment 6

The method of any one of Embodiments 1 through 5, wherein introducing the organic feed material comprises introducing the organic feed material to a chamber in fluid communication with the cathode.

Embodiment 7

The method of any one of Embodiments 1 through 6, wherein introducing an organic feed material to an electrochemical cell comprises introducing the organic feed material to an electrochemical cell comprising a cathode comprising polytetrafluoroethylene.

Embodiment 8

The method of any one of Embodiments 1 through 7, wherein introducing an organic feed material to an electrochemical cell comprises introducing the organic feed material to an electrochemical cell comprising an anion exchange membrane comprising a polymer functionalized with one or more amines.

Embodiment 9

The method of any one of Embodiments 1 through 8, wherein introducing an organic feed material to an electrochemical cell comprises introducing the organic feed material to an electrochemical cell comprising an anion exchange membrane comprising one or more fluorinated polymers or one or more chlorinated polymers.

Embodiment 10

The method of any one of Embodiments 1 through 9, wherein passing a current through the membrane electrode assembly to convert molecules in the organic feed material to a reduced product comprises generating hydrogen proximate the cathode.

Embodiment 11

The method of any one of Embodiments 1 through 10, wherein passing a current through the membrane electrode assembly to convert molecules in the organic feed material to a reduced product comprises generating hydrogen from water proximate the cathode.

Embodiment 12

The method of any one of Embodiments 1 through 11, wherein introducing an organic feed material to an electrochemical cell comprises introducing the organic feed material to an electrochemical cell comprising a cathode comprising a hydrophobic material.

Embodiment 13

The method of any one of Embodiments 1 through 12, further comprising introducing a feed medium to the anode, the feed medium comprising a material selected from the group consisting of water, organic materials, chloride, or chlorine gas.

Embodiment 14

A method of forming a membrane electrode assembly comprising forming an ink mixture comprising carbon, a resin, and polytetrafluoroethylene, providing droplets of the ink mixture on a substrate to form a decal, and disposing the decal in contact with an anion exchange membrane.

Embodiment 15

The method of Embodiment 14, wherein forming an ink mixture comprises forming a mixture comprising the carbon, the resin, and water.

Embodiment 16

The method of Embodiment 14 or Embodiment 15, wherein forming an ink mixture comprises forming a mixture having a weight ratio of the carbon to the resin from about 2:1 to about 10:1.

Embodiment 17

The method of any of Embodiments 14 through 16, wherein providing droplets of the ink mixture on a substrate comprises providing droplets of the ink mixture having a volume between about 1 μl and about 20 pl.

Embodiment 18

The method of any of Embodiments 14 through 17, further comprising air-drying the droplets of the ink mixture.

Embodiment 19

The method of any of Embodiments 14 through 18, wherein disposing the decal in contact with an anion exchange membrane comprises hot-pressing the decal against the anion exchange membrane.

Embodiment 20

The method of Embodiment 19, wherein hot-pressing comprises applying a pressure of at least 1 MPa to the decal.

Embodiment 21

The method of Embodiment 19 or Embodiment 20, wherein hot-pressing comprises maintaining the decal and the anion exchange membrane at a temperature of between 90° C. and 120° C.

Embodiment 22

The method of any of Embodiments 14 through 21, further comprising forming a second decal and disposing the second decal in contact with the anion exchange membrane at a surface on an opposite side of the anion exchange membrane as the decal.

While the present invention has been described herein with respect to certain illustrated embodiments, those of ordinary skill in the art will recognize and appreciate that it is not so limited. Rather, many additions, deletions, and modifications to the illustrated embodiments may be made without departing from the scope of the invention as hereinafter claimed, including legal equivalents thereof. In addition, features from one embodiment may be combined with features of another embodiment while still being encompassed within the scope of the invention as contemplated by the inventors. Further, embodiments of the disclosure have utility with different and various reactions. 

What is claimed is:
 1. A method for electrochemical hydrogenation, the method comprising: introducing an organic feed material to an electrochemical cell, the electrochemical cell comprising a membrane electrode assembly comprising: an anion exchange membrane; a cathode in electrical contact with a first side of the anion exchange membrane; and an anode in electrical contact with a second side of the anion exchange membrane opposite the first side of the anion exchange membrane; and passing a current through the membrane electrode assembly to convert molecules in the organic feed material to a reduced product comprising reduced molecules containing a higher proportion of hydrogen than the organic feed material.
 2. The method of claim 1, wherein passing a current through the membrane electrode assembly comprises passing a current through the membrane electrode assembly at a temperature of between about 0° C. and about 100° C.
 3. The method of claim 1, wherein passing a current through the membrane electrode assembly comprises passing a current through the membrane electrode assembly at a pressure of less than about 1 MPa.
 4. The method of claim 1, wherein passing a current through the membrane electrode assembly comprises passing hydroxide ions through the anion exchange membrane from the cathode to the anode.
 5. The method of claim 1, wherein introducing the organic feed material comprises flowing the organic feed material continuously into the electrochemical cell.
 6. The method of claim 1, wherein introducing the organic feed material comprises introducing the organic feed material to a chamber in fluid communication with the cathode.
 7. The method of claim 1, wherein introducing an organic feed material to an electrochemical cell comprises introducing the organic feed material to an electrochemical cell comprising a cathode comprising polytetrafluoroethylene.
 8. The method of claim 1, wherein introducing an organic feed material to an electrochemical cell comprises introducing the organic feed material to an electrochemical cell comprising an anion exchange membrane comprising a polymer functionalized with one or more amines.
 9. The method of claim 1, wherein introducing an organic feed material to an electrochemical cell comprises introducing the organic feed material to an electrochemical cell comprising an anion exchange membrane comprising one or more fluorinated polymers or one or more chlorinated polymers.
 10. The method of claim 1, wherein passing a current through the membrane electrode assembly to convert molecules in the organic feed material to a reduced product comprises generating hydrogen proximate the cathode.
 11. The method of claim 1, wherein passing a current through the membrane electrode assembly to convert molecules in the organic feed material to a reduced product comprises generating hydrogen from water proximate the cathode.
 12. The method of claim 1, wherein introducing an organic feed material to an electrochemical cell comprises introducing the organic feed material to an electrochemical cell comprising a cathode comprising a hydrophobic material.
 13. A method of forming a membrane electrode assembly, comprising: forming an ink mixture comprising carbon, a resin, and polytetrafluoroethylene; providing droplets of the ink mixture on a substrate to form a decal; and disposing the decal in contact with an anion exchange membrane.
 14. The method of claim 13, wherein forming an ink mixture comprises forming a mixture comprising the carbon, the resin, and water.
 15. The method of claim 13, wherein forming an ink mixture comprises forming a mixture having a weight ratio of the carbon to the resin from about 2:1 to about 10:1.
 16. The method of claim 13, wherein providing droplets of the ink mixture on a substrate comprises providing droplets of the ink mixture having a volume between about 1 μL and about 20 μL.
 17. The method of claim 13, further comprising air-drying the droplets of the ink mixture.
 18. The method of claim 13, wherein disposing the decal in contact with an anion exchange membrane comprises hot-pressing the decal against the anion exchange membrane.
 19. The method of claim 18, wherein hot-pressing comprises applying a pressure of at least 1 MPa to the decal.
 20. The method of claim 18, wherein hot-pressing comprises maintaining the decal and the anion exchange membrane at a temperature of between 90° C. and 120° C.
 21. The method of claim 13, further comprising: forming a second decal; and disposing the second decal in contact with the anion exchange membrane at a surface on an opposite side of the anion exchange membrane as the decal. 